METHODS: In vitro antioxidant activity was investigated using 2,2'-diphenyl-1-picrylhydrazyl (DPPH), fluorescence recovery after photobleaching (FRAP), and 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) methods. The antidiabetic and dermatoprotective effects were studied using enzyme inhibitory activities.
RESULTS: Antioxidant tests showed that PLEO has the best activity (ranging from 29.64 ± 3.04 to 73.80 ± 3.96 µg/mL) compared to its main selected molecules (ranging from 74 ± 3.72 to 107.23 ± 5.03 µg/mL). The α-glucosidase and α-amylase assays demonstrated that the elements tested have a promising antidiabetic potential with IC50values ranging from 78.03 ± 2.31 to 116.03 ± 7.42 µg/mL and 74.39 ± 3.08 to 112.35 ± 4.92 µg/mL for the α-glucosidase and α-amylase assays, respectively, compared to the standard drug. For the tyrosinase test, we found that the EOs (IC50 = 57.72 ± 2.86 µg/mL) followed by limonene (IC50 = 74.24 ± 2.06 µg/mL) and α-pinene (IC50 = 97.45 ± 5.22 µg/mL) all exhibited greater inhibitory effects than quercetin (IC50 = 246.90 ± 2.54 µg/mL).
CONCLUSIONS: Our results suggest that the biological activities of PLEO, as well as its main compounds, make them promising candidates for the development of new strategies aimed at improving dermatoprotection and treating diseases associated with diabetes mellitus and oxidative stress.
OBJECTIVE: This study investigates the antidiabetic and antioxidant effects of M. latifolia bark extracts, fractions, and isolated constituents.
MATERIALS AND METHODS: Melicope latifolia extracts (hexane, chloroform, and methanol), fractions, and isolated constituents with varying concentrations (0.078-10 mg/mL) were subjected to in vitro α-amylase and dipeptidyl peptidase-4 (DPP-4) inhibitory assay. Molecular docking was performed to study the binding mechanism of active compounds towards α-amylase and DPP-4 enzymes. The antioxidant activity of M. latifolia fractions and compounds were determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging and β-carotene bleaching assays.
RESULTS: Melicope latifolia chloroform extract showed the highest antidiabetic activity (α-amylase IC50: 1464.32 μg/mL; DPP-4 IC50: 221.58 μg/mL). Fractionation of chloroform extract yielded four major fractions (CF1-CF4) whereby CF3 showed the highest antidiabetic activity (α-amylase IC50: 397.68 μg/mL; DPP-4 IC50: 37.16 μg/mL) and resulted in β-sitosterol (1), halfordin (2), methyl p-coumarate (3), and protocatechuic acid (4). Isolation of compounds 2-4 from the species and their DPP-4 inhibitory were reported for the first time. Compound 2 showed the highest α-amylase (IC50: 197.53 μM) and β-carotene (88.48%) inhibition, and formed the highest number of molecular interactions with critical amino acid residues of α-amylase. The highest DPP-4 inhibition was exhibited by compound 3 (IC50: 911.44 μM).
DISCUSSION AND CONCLUSIONS: The in vitro and in silico analyses indicated the potential of M. latifolia as an alternative source of α-amylase and DPP-4 inhibitors. Further pharmacological studies on the compounds are recommended.